<template>
  <div>
    <router-link
      tag="div"
      to="/"
      class="header-ads"
      v-show="showAbs"
    >
      <div class="iconfont header-ads-back">&#xe624;</div>
    </router-link>
    <div
      class="header-fixed"
      v-show="!showAbs"
      :style="opacitystyle"
    >
      <router-link to="/">
        <div class="iconfont header-fixed-back">&#xe624;</div>
      </router-link>
      景点详情
    </div>
  </div>
</template>

<script>
export default {
  name: 'DetailHeader',
  data () {
    return {
      showAbs: true,
      opacitystyle: {
        opacity: 0
      }
    }
  },
  methods: {
    handleScroll () {
      const top = document.documentElement.scrollTop ||
      document.body.scrollTop || window.pageYOffset
      if (top > 60 ) {
        let opacity = top / 140
        opacity = opacity > 1 ? 1 : opacity
        this.opacitystyle = { opacity }
        this.showAbs = false
      } else {
        this.showAbs = true
      }
    }
  },
   //页面展示的时候去绑定scroll事件
  mounted () {
    window.addEventListener('scroll', this.handleScroll)
  },
   // 页面被隐藏的时候，再去对scroll解绑
  destroyed () {
    window.removeEventListener('scroll', this.handleScroll)
  }
}
</script>

<style lang="stylus" scoped>
  @import '~styles/varibles.styl'
  .header-ads
    position :absolute
    left :.2rem
    top :.2rem
    width :.8rem
    height :.8rem
    line-height :.8rem
    border-radius :.4rem
    text-align :center
    background :rgba(0, 0, 0, .8)
    .header-ads-back
      color :#fff
      font-size :.4rem
  .header-fixed
    z-index :2
    position :fixed
    top :0
    left :0
    right :0
    height :$headerHeight
    line-height :$headerHeight
    text-align :center
    color :#fff
    background :$bgColor
    font-size :.32rem
    .header-fixed-back
      position absolute
      top :0
      left :0
      width :.64rem
      text-align :center
      font-size :.4rem
      color :#fff
</style>
